European Energy Commissioner Guenther Oettinger told reporters the "common ambition" was to clinch "an interim solution" to assure supplies through the cold season.Speaking after talks with his Ukrainian counterpart, Oettinger said he would meet with his Russian counterpart before all three sat down together.Oettinger said he hoped it would be the last of several trilateral meetings, including one in Brussels last week, but told German television ZDF earlier that chances of an agreement here were "50 percent." After last week's meeting broke up, Oettinger had said he hoped for an agreement this week.Russia in mid-June cut supplies to Ukraine, demanding the new pro-Western government in Kiev pay sharply higher prices in advance for new deliveries after it ran up what Moscow claimed was an unpaid bill of $5.3 billion (4.1 billion euros).

A danger sign is displayed near an underground gas storage in the Ukraine village of Opari. Gas talk …

That supply cut heightened concerns that Europe, which gets about a third of its gas from Russia of which about a half transits via Ukraine, could be badly affected by the dispute this winter.Oettinger said he held bilateral talks with Ukrainian Energy Minister Yuri Prodan and the head of Ukraine's Naftogaz before he was to meet his Russian counterpart Alexander Novak and the head of Russia's Gazprom.

"Our common ambition is to come to an interim solution, to come to a winter package ... to solve our security of supply," Oettinger said.

Oettinger said hurdles still had to be cleared, including Ukraine's settling unpaid bills and paying in advance for its purchases.

In order for Russia to resume supplies to Ukraine for the winter, he told ZDF, old bills must be paid, like those from November and December last year as well as for April, May and June this year.